To prevent reflection of outside lights and improve image quality of various display panels such as liquid crystal display panels, cold cathode ray tube panels and plasma displays, being desired is an antireflection film having a low refractive index layer comprising a cured product exhibiting a superior low refractive index property, antiscratching property, coating property and durability.
Surfaces of these display panels are often wiped with gauze impregnated with ethanol or the like to remove adhered fingerprints, dusts etc., and therefore antiscratching property is desired.
In liquid crystal display panels, in particular, an antireflection film is provided on a liquid crystal unit in a state that it is laminated on a polarizing plate. Further, for example, triacetyl cellulose etc. is used as a substrate. An antireflection film using such a substrate usually need to be saponified with an alkaline aqueous solution to increase adhesion when it is adhered to the polarizing plate.
Accordingly, for use in liquid crystal display panels, an antireflection film exhibiting superior durability, especially superior alkali resistance, is desired.
As materials for a low refractive index layer of antireflection films, for example, fluorine resin type paints containing a hydroxyl group-containing fluoropolymer are known, and they are disclosed in JP-A-57-34107, JP-A-59-189108, JP-A-60-67518 and so forth.
However, for such fluorine resin type paints, it is necessary to heat the hydroxyl group-containing fluoropolymer and a curing agent such as a melamine resin in the presence of an acidic catalyst to crosslink them for curing a coated film. Therefore, such fluorine resin type paints have problems depending on the heating conditions that curing time is extremely extended or types of usable substrates are limited.
Furthermore, the obtained coated film also has problems of poor antiscratching property and durability, although it exhibits superior weather resistance.
Therefore, to solve the above problems, JP-B-6-35559 proposes a paint composition containing an unsaturated group- and fluorine-containing vinyl polymer obtained by reacting an isocyanate group-containing unsaturated compound having at least one isocyanate group and at least one addition-polymerizable unsaturated group and a hydroxyl group-containing fluoropolymer at an isocyanate group/hydroxyl group number ratio of 0.01 to 1.0.
However, in the aforementioned patent publication, the unsaturated group- and fluorine-containing vinyl polymer is prepared without using the isocyanate group-containing unsaturated compound in an amount sufficient for reacting all of the hydroxyl groups in the hydroxyl group-containing fluoropolymer so as to intentionally leave unreacted hydroxyl groups in the polymer.
Therefore, although a paint composition containing such a polymer can be cured at a low temperature in a short period of time, a curing agent such as a melamine resin must be further used to react the remaining hydroxyl groups for curing. Further, the coated film obtained in the aforementioned patent publication has a problem that coating property and antiscratching property cannot be considered sufficient.
Accordingly, an object of the present invention is to provide an ethylenically unsaturated group-containing fluoropolymer which exhibits superior antiscratching property, coating property and durability, a curable resin composition and an antireflection film using the same.